The brain requires an uninterrupted supply of blood to grow and function so much so that interruption of blood flow caused by stroke or injury often causes permanent disability. The network of vessels that carry blood to and from neural tissue are formed during development and are maintained throughout the lifetime of an individual. The growth and stability of this system depends upon important communication between the blood vessel and the surrounding milieu, which includes neural crest-derived cells like pericytes and meningeal fibroblasts and the brain itself. Experiments in this proposal utilize Foxc1 mutant mice, which have defects in both vascular and brain development, to gain further insight into how the brain vasculature forms. This approach is unique because Foxc1 does not have a cell autonomous role in brain endothelial cell (EC) function. Rather, the defects in vascular development likely stem from the loss of important developmental cues that emanate from tissues and cells adjacent to the blood vessels. One goal of this grant is to determine how absence of the meninges and defects in neocortical development differentially contribute to vascular malformations in Fox1 mutant mice. We will be focusing on how potential disruption of neural derived angiogenic cues like Wnt and VEGF alters vascular development in the perineural and neocortical vascular plexuses. Foxc1 is expressed by brain pericytes but its function in this cell-type is unknown. Analysis of a pericyte conditional Foxc1 mutant mice suggest that Foxc1 plays in integral role in pericyteendothelial interactions, specifically in regulating cell proliferation of both cell types. We propose to use genetic profiling and in vitro experiments in to identify pericyte derived factors downstream of Foxc1 and determine how they may regulate cell proliferation in the neural vasculature.